Fix: retry onFreedomPurchaseStateChanged delivery to survive WebView-not-ready race

Root cause found: evaluateWebViewJs() silently no-ops if webViewInstance is
null or the page/JS context isn't fully attached at that exact moment
(webViewInstance?.post{...} just does nothing). The Freedom purchase
callback was previously fired exactly once, right when Google Play's
billing callback returns - often right as the Activity is still
transitioning back from the Play billing bottom sheet, i.e. exactly when
the WebView is least likely to be reliably attached.

If that single delivery was dropped, nothing resent it: queryActiveSubscriptions()
on the next onResume only re-sends the callback when
'!TrialManager.isFreedomPurchased(this)' - but the native flag was already
set to true by the original (dropped) handlePurchase() call, so that guard
silently prevented any retry. The WebView was then stuck showing the
Pro-only UI until a full app restart, where onAndroidReady's parameterless
updateDonationCard() finally read the correct native state fresh.

Fix: new evaluateWebViewJsWithRetry() re-sends the same JS up to 5 times
over ~2 seconds. All 4 call sites for onFreedomPurchaseStateChanged now use
it, so a dropped first delivery is very likely followed by a successful one
shortly after, without requiring the user to restart the app.

Author: Fix Bot

app/src/main/kotlin/com/google/ai/sample/MainActivity.kt

@@ -1297,7 +1297,7 @@ class MainActivity : ComponentActivity() {
                             TrialManager.markAsFreedomPurchased(this)
                             TrialManager.markAsPurchased(this)
                             updateTrialState(TrialManager.getTrialState(this, null))
-                            evaluateWebViewJs("window.onFreedomPurchaseStateChanged && window.onFreedomPurchaseStateChanged(true)")
+                            evaluateWebViewJsWithRetry("window.onFreedomPurchaseStateChanged && window.onFreedomPurchaseStateChanged(true)")
                             Log.d(TAG, "handlePurchase Freedom: Stopping TrialTimerService.")
                             val stopIntent = Intent(this, TrialTimerService::class.java)
                             stopIntent.action = TrialTimerService.ACTION_STOP_TIMER
@@ -1313,7 +1313,7 @@ class MainActivity : ComponentActivity() {
                     TrialManager.markAsFreedomPurchased(this)
                     TrialManager.markAsPurchased(this)
                     updateTrialState(TrialManager.getTrialState(this, null))
-                    evaluateWebViewJs("window.onFreedomPurchaseStateChanged && window.onFreedomPurchaseStateChanged(true)")
+                    evaluateWebViewJsWithRetry("window.onFreedomPurchaseStateChanged && window.onFreedomPurchaseStateChanged(true)")
                 }
             } else {
                 Log.w(TAG, "handlePurchase: Purchase is PURCHASED but does not contain any known product ID. Products: ${purchase.products}")
@@ -1372,7 +1372,7 @@ class MainActivity : ComponentActivity() {
                                 TrialManager.markAsFreedomPurchased(this)
                                 TrialManager.markAsPurchased(this)
                                 updateTrialState(TrialManager.getTrialState(this, null))
-                                evaluateWebViewJs("window.onFreedomPurchaseStateChanged && window.onFreedomPurchaseStateChanged(true)")
+                                evaluateWebViewJsWithRetry("window.onFreedomPurchaseStateChanged && window.onFreedomPurchaseStateChanged(true)")
                             }
                             val stopIntent = Intent(this, TrialTimerService::class.java)
                             stopIntent.action = TrialTimerService.ACTION_STOP_TIMER
@@ -1395,7 +1395,7 @@ class MainActivity : ComponentActivity() {
                     if (TrialManager.isFreedomPurchased(this@MainActivity)) {
                         Log.w(TAG, "queryActiveSubscriptions: No active Freedom subscription found by Google Play Billing, but was previously marked. Clearing Freedom mark.")
                         TrialManager.clearFreedomMark(this@MainActivity)
-                        evaluateWebViewJs("window.onFreedomPurchaseStateChanged && window.onFreedomPurchaseStateChanged(false)")
+                        evaluateWebViewJsWithRetry("window.onFreedomPurchaseStateChanged && window.onFreedomPurchaseStateChanged(false)")
                     }
                     if (TrialManager.isPurchased(this@MainActivity)) {
                         Log.w(TAG, "queryActiveSubscriptions: No active subscription found by Google Play Billing, but app was previously marked as purchased. Clearing purchase mark.")
@@ -1701,6 +1701,27 @@ class MainActivity : ComponentActivity() {
         }
     }
 
+    /**
+     * Like [evaluateWebViewJs], but re-sends the same JS a few times with a delay in between.
+     *
+     * Purchase-completion callbacks (e.g. window.onFreedomPurchaseStateChanged) were previously
+     * sent exactly once, right when Google Play's billing callback fires. If webViewInstance was
+     * null or the page/JS wasn't fully attached yet at that exact moment (e.g. because the
+     * Activity was still transitioning back from the Play billing sheet), the single
+     * evaluateJavascript call was silently dropped and the WebView kept showing the old
+     * (pre-purchase) state until the next full app restart, even though the native purchase
+     * flag was already set correctly. Retrying a few times over a couple of seconds makes
+     * delivery robust without needing a full native rewrite of the purchase flow.
+     */
+    fun evaluateWebViewJsWithRetry(js: String, attempts: Int = 5, delayMs: Long = 400L) {
+        lifecycleScope.launch {
+            repeat(attempts) { attempt ->
+                evaluateWebViewJs(js)
+                if (attempt < attempts - 1) kotlinx.coroutines.delay(delayMs)
+            }
+        }
+    }
+
     /**
      * Escapes a string so it can be safely embedded inside a single-quoted JS string literal
      * passed to [WebView.evaluateJavascript]. Delegates to [WebViewBridge.jsEscape] so both